Ignition system



Feb. 2, 1965 A. M. SKELLETT 3,168,086

IGNITION SYSTEM Filed May '7, 1965 T mum." Z7

1 INVENTOR. a 44 44 4.43527" /1 SKELLETT C/U/F/QE/VT BY fi W g M/c; W 8/, M 05am ATTORNEYS United States Patent 3,168,886 IGNITIUN SYSTEM Albert M. Sslreilett, Madison, N.J., assignor to Tang-Sol Electric inc, a corporation of Delaware Filed May 7, 1963, Ser. No. 273,665 Claims. (Cl. 123148) This invention relates to an ignition system for internal combustion engines. It employs a pressure-sensitive transistor to develop a series of voltage pulses which can be applied through a distributor to a set of spark plugs. The invention has particular reference to an ignition system which uses no breaker contacts for making and breaking an electric circuit.

Many ignition systems have been devised and used which generate high voltage pulses for use in spark plugs positioned in the piston chambers of internal combustion engines. All of these systems use breaker contacts which either make or break a circuit to provide a voltage pulse which results in a high voltage for bridging the spark gap electrodes. The present invention does not employ contacts which either make or break a circuit. Instead, a current pulse is generated by the pressure applied by a stylus which is mounted in contact with a pressure-sensitive transistor. It has been known for some time that a change of current is produced when pressure is applied to the emitter or collector electrodes of a transistor. This change of current may be employed to produce an electric pulse which can be amplified to produce a spark for exploding the gases in a piston chamber. The elimination of breaker contacts eliminates the pitting and corrosion generally experienced in the usual ignition systems. The result is longer life, reduction of service requirements, and more dependable results.

One of the objects of this invention is to provide an improved ignition system which avoids one or more of the disadvantages and limitations of prior art systems.

Another object of this invention is to eliminate the wear due to sparking and pitting of breaker contacts in an ignition system.

Another object of this invention is to reduce the friction and mechanical wear by lowering the pressures usually employed in conventional ignition systems.

Another object of the invention is to increase the reliability of ignition systems.

Another object of the invention is to produce reliable ignition performance at all speeds including starting and idling speeds.

Another object of the invention is to eliminate the make and break contacts.

Another object of the invention is to eliminate sparking at a pair of breaker contacts and therefore reduce the fire hazard often associated with internal combustion engines.

Another object of the invention is to increase the life of ignition systems.

The invention comprises an ignition system for internal combustion engines which includes a pressure-sensitive transistor having base, collector, and emitter electrodes. A stylus is mounted in contact with one of the transistor electrodes and a rotatable cam is employed to exert pressure on the stylus each time a voltage pulse is to be transmitted to an engine spark plug. The system also includes a step-up transformer coupled between the transistor and the spark plug assembly. The primary winding of the transformer is coupled to two of the transistor electrodes for receiving pulsating current and the secondary winding is connected through a distributor to the spark plugs.

One feature of the invention includes a transistor amplifier stage coupled between the pressure sensitive transistor and the transformer for increasing the amplitude of the current pulses. Another feature of the invention 3,.fi3fi8 5 Patented Feb. 2, 1965 includes an oscillator stage coupled between the pressuresensitive transistor and the transistor amplifier stage. The oscillator stage is biased for non-oscillatory operation in order to provide for proper timing. The relaxation oscillation provides a fast rise time for the current pulse which is triggered by the pressure-sensitive transistor.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

PEG. 1 is a top view of the pressure-sensitive transistor showing the stylus and the cam which operates it.

FIG. 2 is a side view of the structure shown in FIG. 1.

FlG. 3 is a schematic diagram of connections showing the pressure-sensitive transistor, the stylus, a coupling transformer, and an array of spark plugs.

FIG. 4 is a schematic diagram similar to FIG. 3 but including a transistor amplifier stage between the pressure-sensitive transistor and the step-up transformer.

FIG. 5 is a schematic diagram of connections similar to FIG. 4 but including a unijunction transistor coupled between the pressure-sensitive transistor and the amplifier stage.

FIG. 6 is a graph showing a wave form produced by a portion of the circuit shown in FIG. 5.

Referring now to FIGS. 1 and 2, a pressuresensitive p-n-p transistor 10 is shown mounted on a support 11 which is secured to a base 12:. At the center of the base a shaft 13 is journaled for rotating a cam The shaft 13 is coupled to a portion of the engine so that the cam 14 will exert pressure on a cam follower 15 to press a stylus 16 onto the transistor 1t Many types of coupling devices can be used between the cam 14- and the stylus 16. It has been found safer to use a resilient coupling means such as that shown in FIGS. 1 and 2 wherein a stiff bar 17 connects the cam follower 15 and the stylus 16. Bar 17 is connected by a spring 18 to a support 29 which is secured to base 12. An auxiliary spring 21. secured to a stud 22 presses against bar 17 to maintain contact of stylus 16 with transistor 19 at all times. Whenever the cam 14 revolves, a sharp pressure pulse is periodically exerted on follower 15' which is transmitted immediately to stylus 16 and transistor 19 thereby lowering the current flowing between the transistor emitter and collector electrodes. It is obvious that other types of mechanical transmitting means may be used to exert pressure on the transistor in synchronism with the movements of the engine crank shaft and the pistons carried by it.

Referring now to FIG. 3, stylus 16 is shown in contact with the emitter of transistor 19 (pm-p). The best results are obtained when the stylus is in contact with the emitter 23 but the electrodes may be reversed and the stylus may be in contact with collector 24. The emitter and collector electrodes are connected in series with the primary winding 25 of a transformer 26 and a source of direct current power 27. The secondary 28 of transformer 26 is connected directly to the usual distributor 30 and spark plugs 31. The base of transistor 10 is connected to the negative terminal of the source through a self-biasing circuit 32 which maintains the potential of the base at the proper value.

The operation of this circuit is as follows: When there is little or no pressure exerted by the stylus 16 on transistor 10, a maximum current fiows from the battery 27 through primary winding 25 and transistor It This current produces magnetic fiux in the core of transformer 26. When cam 14 exerts a pressure on the stylus and on the transistor, the effective resistance is increased and the current is reduced sharply so that the magnetic field produced by the direct current flow in the transformer 3 is reduced almost to zero and a high voltage pulse is produced in the secondary winding 28. The high voltage pulse is transmitted through distributor St) to one of the spark plugs 31 to ignite the explosive mixture.

Referring now to FIG. 4, the same elements are shown except that a transistor amplifier stage 33 has been coupl d between the pressure-sensitive transistor and the priinary winding 25 of the step-up transformer 25. This stage includes a transistor 34 having its collector connected to one terminal of the primary winding 25 while the emitter is connected through a resistor to the positive terminal of battery 27. The base of transistor 34 is connected directly to collector 24 of transistor it). The operation of this device is the same as described above except that the amplifier stage 33 increases the amplitude of the current pulses applied to the transformer.

The circuit diagram shown in FIG. is the same as that shown in FIG. 4 except that the pressure-sensitive transistor MA is an n-p-n type and that a unijunction transistor 35 has been between the pressure-sensitive transistor A and the amplifier stage 33. The unijunction transistor has its emitter electrode connected to the midpoint of a voltage divider composed of resistors 36 and 37, the terminals of which are connected to the terminals of the source of potential 27. A capacitor 4%, in conjunction with resistors 41 and 42, forms a relaxation circuit which is biased to be in a condition which is below the state of oscillation. When the pressure-sensitive n-p-n transistor ltlA receives a decrease of pressure from its stylus, a larger current fiows through the collector electrode, thereby applying a negative pulse to the B terminal of the unijunction transistor. This pulse triggers the unijunction transistor to the on or conductive condition and causes an abrupt lowering of the potential of emitter 43. Capacitor 4t? discharges with the result that the current in the collector circuit of the n-p-n transistor 34A is abruptly reduced. The reduction in current in winding produces the same results as explained above.

The graph shown in FIG. 6 indicates the amplitude of the control pulses applied to the base of transistor 34A. The current through the transformer primary follows a similar wave form. It should be noted that the current decay 44 is quite fast, a condition which produces a steeper rise in the spark plug voltage, and results in better operation, especially if the spark plug is not clean.

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limitations are to be determined from the scope of the appended claims.

I claim:

1. An ignition system for internal combustion engines comprising; a pressure-sensitive transistor including base, collector, and emitter electrodes; a stylus mounted in contact with one of said transistor electrodes; a rotatable cam coupled to a portion of said engine and adapted to exert pressure on the stylus each time a voltage pulse is to be transmitted to an engine spark plug; and a step-up transformer coupled between said transistor and the spark plugs, the primary winding of said transformer coupled to said transistor electrodes for receiving pulsating current pulses therefrom.

2. An ignition system for internal combustion engines comprising; a pressure-sensitive transistor including base, collector and emitter electrodes; a stylus mounted in contact with one of said transistor electrodes; a rotatable cam coupled to a portion of said engine and adapted to rotate in synchronism with a main power shaft; said cam adapted to exert pressure on the stylus each time a voltage pulse is to be transmitted to an engine spark P d a Stepp transformer coupled between said transistor and the spark plugs, the primary winding of said transformer connected in series wi h the collector electrode, a source of potential, and the emitter electrode.

3. An ignition system for internal combustion engines comprising; a pressure-sensitive transistor including base, collector, and emitter electrodes; a stylus mounted in contact with one of said transistor electrodes; a rotatable cam secured to a shaft which is turned in synchronism with a main engine power shaft; said cam adapted to exert pressure on the stylus and alter the collector-emitter resistance whenever a voltage pulse is to be transmitted to an engine spark plug; and circuit means connected between the transistor and the spark plugs which transforms said change in resistance into a high voltage pulse which is adapted to explode an explosive mixture, said circuit means including a distributor, a high voltage transformer, and a source of direct current power connected between the emitter and collector electrodes in series with a primary winding of said transformer.

4. An ignition system as claimed in claim 3 wherein a transistor amplifier is coupled between said pressuresensitive transistor and said primary winding for amplifying the current pulses produced by the pressure-sensitive transistor.

5. An ignition circuit as claimed in claim 3 wherein a partially unstable relaxation circuit is coupled between said pressure-sensitive transistor and said primary winding for producing a faster rise time in the voltage pulse when the current in the collector circuit is decreased by pressure exerted by the stylus.

6. An ignition system for internal combustion engines comprising; a pressure-sensitive transistor including base, collector, and emitter electrodes; a stylus mounted in contact with one of said transistor electrodes; a rotatable cam coupled to a portion of said engine and adapted to exert pressure on the stylus each time a voltage pulse is to be transmitted to an engine spark plug; a step-up transformer having a primary and secondary winding with its primary winding connected to said collector electrode in series with a source of direct current power; and an engine distributor connected between the transformer secondary winding and said spark plugs.

7. An ignition system for internal combustion engines comprising; a pressure-sensitive transistor including a collector electrode on one side and an emitter electrode on the other side; mounting means for said transistor for securing the collector electrode to an immovable support; a stylus mounted in contact with said emitter electrode for exerting pressure thereon; a rotatable cam coupled to a portion of the engine and adapted to apply pressure on the stylus each time a voltage pulse is to be transmitted to an engine spark plug; and electrical coupling means connected between said transistor and said spark plugs; said coupling means including a transformer, a source of direct current power, and a rotary distributor run by said portion of the engine.

8. An ignition system as claimed in claim 7 wherein the emitter electrode is secured to the support and the stylus is in contact with the collector.

9. An ignition system as claimed in claim 7 wherein a transistor amplifier is coupled between said pressuresensitive transistor and said transformer.

10. An ignition system as claimed in claim 9 wherein a unijunction transistor is coupled between the pressuresensitive transistor and the transistor amplifier, said unijunction transistor connected to a partially unstable oscillation circuit for producing a faster rise time in the voltage pulse when the current to the collector of the pressure-sensitive transistor is increased by a decrease of pressure exerted by the stylus.

No references cited. 

1. AN IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES COMPRISING; A PRESSURE-SENSITIVE TRANSISTOR INCLUDING BASE, COLLECTOR, AND EMITTER ELECTRODES; A STYLUS MOUNTED IN CONTACT WITH ONE OF SAID TRANSISTOR ELECTRODES; A ROTATABLE CAM COUPLED TO A PORTION OF SAID ENGINE AND ADAPTED TO EXERT PRESSURE OF THE STYLUS EACH TIME A VOLTAGE PULSE IS TO BE TRANSMITTED TO AN ENGINE SPARK PLUG; AND A STEP-UP TRANSFORMER COUPLED BETWEEN SAID TRANSISTOR AND 